Have you actually checked to verify that you have front output when in 2HI mode? Most tcases do not.
except ath "NP (new possess) 203" has
4LOW LOCK
4LOW
N
4HI
4HI LOCK
5 DETENT SHIFTER ALL 4 GO MODES ARE 4WD.
T CASE actually acts like an open differential. Power goes the path of least resistance eg: Stripped the drive splines on the right front stub shaft/ huband had to shift from (4 hi open)2wd to(4hi lock) 4wd to get move the truck. Truck in in gear 2wd hi and going nowhere just a grinding noise from the right front wheel.
These were used by Ford Gm and Dodge for the 70's and 80's aka all full size domestic 4x4's smaller than duce and a hafe. This makes them common and cheep. 2.0:low
Some 203's have factory or aftermarket parttime kits that included lockouts for the front axle. That actually decouple the chain drive and are thire for 2x4 with this shift patern:
4LO
2LO rear only
N
2HI rear only
4HI
The 45mph recommendation is a NHTSA/Auto Mfr recommendation based on the fact that if you needed 4wd, you probably shouldn't be going more than 45mph anyway, not to mention that tire slip increases at higher speeds, and true 4wd systems don't steer well when in use, thus making a very dangerous situation at higher speeds. It's just plain unsafe, and there is no discussion necessary on that topic.
is this speed for a newer truck in low range with a double overdrive? See above Ive had my 79 Chevrolet k-20 over 110mph @~5000rpm with ~2000rpm left, was fast enough for 33's and 4"lift 6000lbs truck , on CA99 befor I stripped the hub. Aka full-time4×4.
The shorter ratios, I was wrong about. They would mean nothing in your case, since you're driving on a 1:1 ratio from front to rear output shafts.
after I spit the part-time kit out the side of the tail housing of my np203 and cracked the bellhousing
Attachment 19917were the part-time kit attempted to escape my np203
Attachment 19916 rear mount flang of the th400
Attachment 19915 bell cracked 70% I finished it off with a hammer befor recycling them both.
In most cases, 4Lo is not recommended for use on any surface that isn't soft. As such, you shouldn't be outside of low gear when using it.
>5mph with a 2.48 1st ×2.0 low ×4.10 rear=20.33:final GM recommendation is 25mph, ~3000rpm, in 3rd I hit red line at 35mph. A first of 7.xx SM 420(from the 60's /SM435 (used through the 90's)= 1mph red line . This first gear recommendation is Ludacris IMHO.
These really shouldn't have to be discussed... talk to a few offroaders that have had to limp home on FWD only, and you'll figure out that they're practices that should be adhered to fairly well.
The speed limitations for 4wd mode don't apply if you're using the motor in place of the front axle connection, because you won't be turning all 4 tires under power, so you can disregard that part.
Mounting the motor inline with the rear driveshaft DOES NOT subject it to suspension abuse. I'm not sure where you came up with that...
Using that configuration would also allow you to remove the motor from the driveline by removing a few bolts and replacing the original drive shaft... not sure how hard you think that is, but if you find it difficult to R&R a driveshaft with a carrier bearing, you probably shouldn't even be thinking about this type of mod.
Mounting it from the front input of the xfer case does not give you a "gear reduction for low speed use."
a twin stick NP205 canas you'll be driving the rear shaft at a 1:1 speed through the xfer case, no matter what gear you're in, unless you have two differential sizes in the front and rear, which is highly unlikely. If both axles have the same differential speed, you'll have the same 1:1 ratio in the t-case no matter what range you select, as this is the nature of 4wd... turn front and back so they match each other based on the engine's input...
After blowing my TH400/NP203 combo I installed a custom TH400/NP 205 twin stick with a 800stall to hold up to my ~400hp engine no mud boggen,just rock crawling ,hi way and , Wood hauling .
The twin stick comes in 2 version; 1 with the stock lock out matching your discretion of 1:1 . 2 extreme no lockout front low/ rear hi 2:1 3000@60mph rear /6000 frontor vica verca.
The extreme is for a form of "DIG" insted of just putting the rear in N it s powered at a different rate to facilitate turnning sharper than other wise posable, and for face climbing.
As i said "Extreme " not hi way
I ordered myself option 1 with lockout to protect from friends using my truck and a MSD 6 digital with the secondary rev limiterset to 3000rpm on a hiden toggle.